Mucosal immunizations, such as nasal delivery of vaccines, have a number of advantages over classical parenteral vaccinations. They are needle-free, are less prone to contamination, depend less on trained medical or paramedical staff, may induce both systemic and mucosal immunity and are probably more suitable to protect against mucosal infections. However, most antigens are poor immunogens when given nasally and require the addition of potent mucosal adjuvants. One of the most potent mucosal adjuvant is cholera toxin or the closely related Escherichia coli heat-labile toxin and their detoxified derivatives. Unfortunately, the addition of this adjuvant to nasal vaccine formulations has been associated with Bell's palsy (Mutsch et al., 2004) and can therefore not be used in humans.
The authors of the present invention have recently developed an attenuated live nasal vaccine candidate against pertussis (Mielcarek et al., 2006), which has now successfully completed a first-in-man phase I safety trial (Thorstensson et al., in preparation). The concept of this candidate vaccine was based on the finding that natural infection with Bordetella pertussis via aerosol exposure is able to induce strong systemic B and T cell responses, even in very young infants (Mascart et al., 2003), as well as mucosal immunity. In addition, previous studies in non-human primates have led to the conclusion that “ultimate protection against whooping cough probably best follows a live B. pertussis inoculation” (Huang et al., 1962).
The B. pertussis strain was attenuated based on the knowledge of the molecular mechanism of B. pertussis virulence (Locht et al., 2001) and constructed by genetically inactivating pertussis toxin, by deleting the dermonecrotic toxin gene and by exchanging the ampG gene of B. pertussis by Escherichia coli ampG, thereby abolishing the production of the tracheal cytotoxin. In preclinical models, this vaccine candidate, named BPZE1, showed excellent safety (Mielcarek et al., 2006, 2010; Skerry et al., 2009; Kavanagh et al., 2010; Li et al., 2010) and induced fast, strong and long-lasting immunity upon a single nasal administration (Feunou et al., 2010).
Moreover, it was surprisingly uncovered that the BPZE1 strain, when nasally administered to mice was capable of eliciting a protective response against allergic and inflammatory conditions of the airways tract namely asthma and furthermore against topic allergies.
Reveneau et al. disclose a genetically attenuated Bordetella strain deficient in toxin production and expressing a hybrid protein comprising the N-terminal fragment of filamentous haemagglutinin (FHA) and protective tetanus toxin fragment C (TTFC), which strain does not produce mature FHA.
Coppens et al. disclose a genetically attenuated Bordetella strain deficient in toxin production and expressing a hybrid protein comprising the N-terminal fragment of filamentous haemagglutinin (FHA) and TbpB of N. meningitis, which strain does not produce mature FHA.
Alonso et al. discloses a genetically attenuated Bordetella strain deficient in toxin production and expressing a hybrid protein comprising the N-terminal fragment of filamentous haemagglutinin (FHA) and the HtrA protein of non typeable Haemophilus influenza, which strain does not produce mature FHA
U.S. Pat. No. 6,841,358 discloses a genetically attenuated Bordetella strain deficient in toxin production and expressing a hybrid protein comprising the N-terminal fragment of filamentous haemagglutinin (FHA) and a model peptide of Sm28 GST of Schistosoma mansoni, which strain is deficient in the production of mature FHA
However, the fhaB gene was not deleted for the purpose of increasing immunogenicity but the deletion was only coincidental and an intrinsic feature of the strain used as a carrier for the production of the heterologous antigen.
BPZE1 has subsequently been considered as a vector for the expression of heterologous protective antigens, in order to develop multivalent nasal vaccines able to protect simultaneously against several different pathogens. The neutralizing peptide SP70 from enterovirus 71 has been surface exposed and secreted by BPZE1 as a hybrid protein with filamentous haemagglutinin (FHA), and using the secretion machinery of FHA (Ho et al., 2008). Similarly, the FHA machinery was also used to secrete and expose the ectodomain of matrix protein 2 from the influenza A virus by BPZE1 (Li et al., 2011). Although systemic and local IgG and IgA responses could be elicited to the heterologous antigens upon administration of the recombinant BPZE1 derivatives, the immune responses to the passenger antigens were usually modest at best.
Upon trying to resolve the problem of poor immunogenicity obtained with the BPZE1 constructs, it was surprisingly discovered by the inventors that immunogenicity could be considerably increased when the native fhaB gene encoding the naturally occurring FHA protein was deleted or otherwise inactivated.
Moreover the strains thus obtained showed a substantially increased immunogenicity despite the anti-inflammatory properties of the native attenuated strain of Bordetella pertussis as evidenced by their activity against asthma and allergic diseases. Consequently the instant invention solves the problem for a vaccine for mucosal application, which is safe and capable of eliciting a potent immune response against an antigen present in a pathogen responsible for systemic or mucosal infections, including pathogens responsible for infections of the upper or lower respiratory tract.